It is well known that water insoluble oils such as mineral oil or fatty unsaturated oils are not fully acceptable for working metals from the point of view of cooling efficiency. Early patents like U.S. Pat. No. 3,929,656 to Flis issued Dec. 30, 1975, disclose a typical oil based system made up of 60-90% mineral oil, 5-30% unsaturated fatty oil and 3-15% paraffin oil. Emulsion type lubricants based upon these oils have been used conventionally for plastic deformation processes including but not limited to hot rolling of aluminum, the manufacture of aluminum cans by drawing and ironing, the cold rolling of steel and so forth. These conventional emulsions contain, as an emulsifier, an anionic soap, a nonionic surfactant, e.g., a sorbitol ester of alkoxylated alcohol, and other additives. The products used in these processes are typically liquid at ambient temperatures and are of high molecular weight to allow for the needed lubrication properties. In order to get a lubricating material that is effective and liquid, the products of interest have been based upon unsaturated hydrophobes like oleic, linoleic, and tall oil acids. U.S. Pat. No. 3,945,930 to Sugiyma issued Mar. 23, 1976, discloses a typical emulsion system made up of a nonionic fatty acid ethoxylate, and oil soluble unsaturated fatty triglyceride and a corrosion inhibitor based upon a phosphate ester. U.S. Pat. Nos. 4,042,515 and 4,075,393 describe a dimer acid unsaturated fatty acid ester used in an emulsion system for metal lubrication. Hydrophobic coatings applied to pre-formed aluminum are described in U.S. Pat. No.4,099,989. U.S. Pat. No. 4,243,537, No. 4,362,634 and No. 4,581,152 wherein an unsaturated water dispersible fatty acid alkoxylate and an alkanolamine soap are used in drawing compounds.
While the above materials function fairly well as lubricants, they are subject to oxidation and development of rancidity. Also the double bonds needed for the desired liquidity, are oxidized to lower molecular weight aldehydes, ketones and condensation products which react to form by-products imparting objectionable color, odor and taste. These deleterious results occasioned by by-products, even in minute concentration as low as parts per billion, persist after repeated washings. Such objectionable properties are particularly unacceptable in applications where a beverage or other comestible products are packaged in metal containers which have been formed using such synthetic lubricants during processing. The brewing industry has recenlty introduced a maximum unsaturation level, indicated by iodine value of 3 mg KOH/gram, for any material used as synthetic lubricants during the formation of their metal containers.
It is therefore an object of the present invention to overcome the above lubricant deficiencies and to provide a convenient, efficient and economical process for lubrication during metal forming.
Another object of this invention is to provide a group of compounds having excellent lubricating properties and low levels of unsaturation.
Another object is to provide lubricants of relatively high molecular weight which retain fluidity at temperatures suitable for metal working.
Still another object is to provide a lubricating composition particularly useful in the formation of aluminum cans and sheet metal.
These and other objects of the invention will become apparent from the following description and disclosure.